android Camera 如何判断当前使用的摄像头是前置还是后置
现在 android 平台的智能手机一般都标配有两颗摄像头。在 Camera 中都存在摄像头切换的功能。
并且有一些功能前后置摄像头上会有所不同。譬如人脸检测,人脸识别,自动对焦,闪光灯等功能,
如果前置摄像头的像素太低,不支持该功能的话,就需要在前置摄像头上关掉该 feature.
那么是如何判断并切换前后置摄像头的呢?
我们先来看下 CameraInfo 这个类,
- /**
- * Information about a camera
- */
- public static class CameraInfo {
- /**
- * The facing of the camera is opposite to that of the screen.
- */
- public static final int CAMERA_FACING_BACK = 0;
- /**
- * The facing of the camera is the same as that of the screen.
- */
- public static final int CAMERA_FACING_FRONT = 1;
- /**
- * The direction that the camera faces. It should be
- * CAMERA_FACING_BACK or CAMERA_FACING_FRONT.
- */
- public int facing;
- /**
- * <p>The orientation of the camera image. The value is the angle that the
- * camera image needs to be rotated clockwise so it shows correctly on
- * the display in its natural orientation. It should be 0, 90, 180, or 270.</p>
- *
- * <p>For example, suppose a device has a naturally tall screen. The
- * back-facing camera sensor is mounted in landscape. You are looking at
- * the screen. If the top side of the camera sensor is aligned with the
- * right edge of the screen in natural orientation, the value should be
- * 90. If the top side of a front-facing camera sensor is aligned with
- * the right of the screen, the value should be 270.</p>
- *
- * @see #setDisplayOrientation(int)
- * @see Parameters#setRotation(int)
- * @see Parameters#setPreviewSize(int, int)
- * @see Parameters#setPictureSize(int, int)
- * @see Parameters#setJpegThumbnailSize(int, int)
- */
- public int orientation;
- };
见名知义,它就是一个 Camera 信息类。它是通过与屏幕的方向是否一致来定义前后置摄像头的。
与屏幕方向相反即为 BACK_FACING_CAMERA
与屏幕方向一致即为 FRONT_FACING_CAMERA
那么在代码中我们是如何获取当前使用的 CamerInfo 呢
- Camera.CameraInfo info = new Camera.CameraInfo();
- Camera.getCameraInfo(cameraId, info);
判断使用是前置还是后置摄像头,可以通过if (info.facing == CameraInfo.CAMERA_FACING_FRONT) 来判断。
当Camera 的实例已经创建了的情况下,则需要通过如下方式来判断。
- CameraInfo info = CameraHolder.instance().getCameraInfo()[mCameraId];
- if (info.facing == CameraInfo.CAMERA_FACING_FRONT) {
- //stopFaceDetection();
- }
也可以通过 if(mCameraId == CameraInfo.CAMERA_FACING_FRONT) 来判断。
其中 mCameraId 是当前使用的 CameraId, 一般前置为1, 后置为 0。